﻿EDIT: I will be adding additional information to the bottom of this post until I do the next one around October 1. Please check back for updates, I'm sure they will be frequent!

As we approach meteorological fall (September 1), I thought it would be a good time to take a long range look at our potential for winter weather for this upcoming 2014-2015 winter season. I'm ready for winter, so I had to share what we currently believe may happen. The outlook is based on the factors that are currently in place, and/or expected to be in place by the time winter arrives. Keep in mind, no one has that crystal ball that will tell us what's going to happen this winter (although if you know of one for cheap, I'm in the market... :-)), but if we take the time to look at similar weather patterns from the past, we can use those analogs to help to predict what may be in store for us in the future.

One of my weather buddies is a weather statistician, particularly regarding Georgia weather. But Larry (aka "Brother Larry" if you've followed my past Patch.com blog) also keeps stats on Nina/Nino events as well as other types of weather information, and has been spot on in the past about statistically analyzing past winter weather seasons and providing probabilities for future events. Fun stuff! Larry has graciously allowed me to quote him about some of the statistical probabilities for the weather this winter in the Atlanta area, so many thanks to Larry and his hard work putting these statistics together.

In Larry's post, he makes reference to several teleconnection indices as well as the ENSO status. Here are some links to those indices that will help you better understand what he's talking about. Click on a specific bullet item for further information:﻿

Right now, the highly touted "Super Nino" that many expected to materialize, has not happened and doesn't appear likely to happen. It now appears that a weak to neutral Nino may occur in it's place. Typically, weak El Nino's have brought great winter weather to the southeast (great meaning if you like winter weather!), and I have more on that below in Larry's post.

The PDO has been in a positive phase for the first 6 months of this year, and a +PDO (plus weak Nino) is what we want for winter weather here in the southeast. Note that with a +PDO, or positive phase, the "wintertime Aleutian low is deepened and shifted southward, warm/humid air is advected along the North American west coast and temperatures are higher than usual from the Pacific Northwest to Alaska but below normal in Mexico and the Southeastern United States. Winter precipitations are higher than usual in the Alaska Coast Range, Mexico and the Southwestern United States but reduced over Canada, Eastern Siberia and Australia". Keep in mind that a strong Nino would reduce precipitation here, but a weak one actually increase our chances for winter weather.

Keep these facts in mind as you read Larry's post.

Larry's Winter Weather Statistics for Atlanta...

In his free video from this weekend (click on the link below), Joe Bastardi shows a map with a prediction from WeatherBell.com of a very cold Southeast winter. He has much of the SE US near or even colder than 4 F below normal. In all of the years of following JB, I can't recall a forecast quite that cold for the SE. However, IF there really ends up being a weak Nino fall/winter peak, a +PDO, and a -NAO, I could see this or even colder than this actually happen. Perhaps he is already thinking somewhat along those lines. For Atlanta (KATL), he's going for a little colder than 4 below normal. How cold is that? Well, that would be very close to a top 10 cold winter for Atlanta, with records going back to 1879-1880. The very cold winter of 2009-2010, which was the coldest by a good margin since 1977-1978, was 4.4 F below average. So, JB is going for something similar to 2009-2010 in terms of cold. He's also going for well above average snowfall including ~150% of norm at ATL/RDU (from Atlanta to Raleigh):http://www.weatherbe...y-august-9-201412 Coldest (back to 1879-80) KATL Winters’ ENSO(WEN=weak El Nino | WLN=Weak La Nina) Winter……DJF Temp Anom…ENSO1) 1976-1977……….…..-7.6……WEN2) 1977-1978…………...-6.2………WEN3) 1904-1905……………-5.8……...WEN4) 1962-1963……………-5.8………WLN or NN5) 1935-1936……………-5.7……….NP6) 1963-1964……………-5.7………*WEN or MEN7) 1939-1940………….-5.5…………WEN8) 1901-1902…………...-5.4……….NN9) 2009-2010………….-4.4…….…SEN10) 1885-1886………….-4.3………WEN11) 1894-1885.............-4.3...........WLN12) 1969-1970…….…..-4.1……….WENNote how many weak El Nino's are listed. Also, note 1963-1964, specifically. On the previous version of the NOAA ONI table, it was considered weak. However, it has been revised as moderate. Regardless of the specifics, the general idea is that weak Nino's have been associated with more very cold Atlanta (and SE) winters per instance than any other ENSO state. However, it still needs the help of a +PDO and -NAO to give it the best shot at being very cold per history. Now, 2004-2005 and 2006-2007 were mild overall. I suspect that the +NAO was a major reason. Then again, February of 2007 was quite cold and the NAO did drop to -0.47 that month.*NOTE: Also, notice the relative absence of La Nina (only two Weak La Nina and one was later revised to Neutral N) and the strong tendency toward weak ENSO, in general (Weak El Nino, Weak La Nina, Neutral N, or NP).-----------------------------------------------------------------------------------------------------------------------------*NOTE: It isn't necessarily true that the weak Nino forcing, itself, causes the big cold. Rather, it may very well be that having a weak Nino allows for the best chance for all factors, combined, to allow for the big cold and may allow it to be amplified somehow.From previous 2012 post: To further illustrate my point, there have been 26 December/January/February's since 1899-1900 with a known +PDO/-NAO/-AO. Note these KATL stats for these +PDO/-NAO/-AO winters:1) 6 Weak Nino's: all 6 had negative anomalies that averaged a very impressively cold -5.0 F. A whopping 5 of 6 very cold.2) 10 moderate to strong Nino's: 8 had negative anomalies and 2 had positive anomalies. The ten averaged -1.3 F. Only 1 of 10 very cold.3) 6 neutral ENSO: 3 had negative anomalies and 3 had positive anomalies. The 6 averaged -1.2 F. 2 of 6 very cold.4) 4 Nina: 2 had negative anomalies and 2 had positive anomalies. The 4 averaged -1.3 F. 1 of 4 very cold.In summary, whereas the 6 weak Nino's averaged a very cold -5.0 F and 5 of 6 were very cold including the 2 coldest on record, the 20 others averaged only a modestly cold -1.3 F or about 25% of the weak Nino's negative anomaly magnitude and only 4 of 20 were very cold. So, it is quite evident to me that the weak Nino state, itself, is associated with a strong tendency toward cold winters at Atlanta that tends to pile onto the cold that tends to already be associated with +PDO/-NAO/-AO and is unlike any other ENSO state, including stronger Nino's.

In other words, nothing comes close to beating the weak Nino/+PDO/-NAO/-AO combo for a cold and wet winter in Atlanta.--------------------------------------------*NOTE: Before anyone tries to attribute west based (vs. east based NAO) as being the most important factor for cold Nino winters, note that the very cold 1976-1977 and 1969-1970 were east based while the mild 2004-2005 was west based. 1977-1978 and 2009-2010 were west based while 1963-1964 was neutral based. My point is that I don't see a clear cut correlation for cold unlike what I see for weak Nino's. On the other hand, I suspect there may be a good correlation of heavier precipitation for a west based NAO.West based appears to be the most likely for this winter assuming there is a Nino. For a combo of heavier precipitation and cold, I suspect that west based might be best hope.

Winter Temperatures - Joe Bastardi and WeatherBell

Winter Precipitation - Joe Bastardi and WeatherBell

You can see from Larry's post, it's not any one factor that determines what the winter is going to be like, it's the interaction between all of the different teleconnections (and a little luck) that determines what happens.So for now, it looks like a possibility of below normal winter temperatures with normal to above normal winter precipitation for the Atlanta metro area.

All of this is dependent on the strength of the Nino during the fall and winter season, so as we get closer to winter, I'll have several additional blog post about how all of this is playing out. Look for another one around October 1 and again right around November 1.